Vane pump

ABSTRACT

A vane pump includes a rotor; a plurality of slits that are formed in the rotor, the plurality of vanes being respectively inserted into the plurality of slits in a slidable manner; a cam ring that has a cam face on which tip-ends of the vanes slide by the rotation of the rotor; and pump chambers that are defined by the rotor, the cam ring, and an adjacent pair of the vanes. The plurality of vanes have a plurality of first vanes that are formed by applying a DLC coating on a base material and second vanes that are formed such that the base material is exposed, the first vanes being respectively inserted into at least two adjacent slits of the plurality of slits.

TECHNICAL FIELD

The present invention relates to a vane pump.

BACKGROUND ART

JP1999-230057A discloses a vane pump including a rotor that isaccommodated in a housing and rotationally driven, vanes that move in asliding manner in slits in the rotor, and a cam ring that is arranged atthe outer side of the vanes and forms pump chambers with the rotor, thevanes, and so forth.

SUMMARY OF INVENTION

Because working oil has high viscosity and high viscous resistance in alow-temperature situation, in the vane pump in the low-temperaturesituation, the vanes are prevented from sliding due to the viscousresistance of the working oil. Therefore, at a starting time of the vanepump in the low-temperature situation, the pump chambers are not easilydefined by the vanes. As described above, in the low-temperaturesituation, the starting performance of the vane pump is deteriorated.

An object of the present invention is to improve the startingperformance of a vane pump.

According to one aspect of the present invention, a vane pump includes arotor linked to a driving shaft; a plurality of slits formed in therotor in a radiating pattern to open in an outer circumference of therotor; a plurality of vanes respectively inserted into the plurality ofslits in a slidable manner; a cam ring having an inner circumferentialsurface on which tip-ends of the vanes slide by rotation of the rotor;pump chambers defined by the rotor, the cam ring, and the pair ofadjacent vanes, wherein the plurality of vanes have: a plurality offirst vanes formed by applying DLC coating on a base material; and asecond vane formed such that the base material is exposed, and the firstvanes are respectively inserted into at least two adjacent slits of theplurality of slits.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of a vane pump according to a first embodiment ofthe present invention.

FIG. 2 is a sectional view of the vane pump according to the firstembodiment of the present invention.

FIG. 3 is a front view of the vane pump according to a second embodimentof the present invention.

FIG. 4 is a front view of the vane pump according to a third embodimentof the present invention.

DESCRIPTION OF EMBODIMENTS First Embodiment

An overall configuration of a vane pump 100 according to a firstembodiment of the present invention will be described with reference toFIGS. 1 and 2.

The vane pump 100 is used as a fluid pressure source for a fluidpressure apparatus mounted on a vehicle, such as, for example, a powersteering apparatus, a continuously variable transmission, or the like.In this embodiment, the fixed displacement vane pump 100 using workingoil as working fluid will be described. The vane pump 100 may also be avariable displacement vane pump.

In the vane pump 100, motive force from an engine (not shown) istransmitted to an end portion of a driving shaft 1, and a rotor 2 linkedto the driving shaft 1 is rotated. The rotor 2 is rotated in theclockwise direction in FIG. 1.

As shown in FIGS. 1 and 2, the vane pump 100 includes a plurality ofvanes 3 that are provided so as to be able to reciprocate in the radialdirection relative to the rotor 2, a cam ring 4 that accommodates therotor 2 and has a cam face 4 a serving as an inner circumferentialsurface on which tip-ends of the vanes 3 slide by rotation of the rotor2, a pump body 10 having an accommodating concave portion 10 a foraccommodating the cam ring 4, and a pump cover 11 that is fastened tothe pump body 10 to seal the accommodating concave portion 10 a. Asshown in FIG. 2, the driving shaft 1 is rotatably supported by the pumpbody 10.

As shown in FIG. 1, in the rotor 2, slits 7 having openings in an outercircumferential surface of the rotor 2 are formed in a radiating patternwith predetermined gaps. The vanes 3 are respectively inserted into theslits 7 in a reciprocatable manner. In the slits 7, back pressurechambers 8 into which discharge pressure is guided are defined bybase-end portions of the vanes 3. In addition, the adjacent backpressure chambers 8 are communicated with each other by a back pressuregroove 8 a formed in the pump cover 11 (see FIG. 2).

In the vane pump 100, twelve vanes 3 are provided. The vanes 3 arepushed in the directions in which the vanes 3 are drawn out from theslits 7 by the pressure of the working oil guided into the back pressurechambers 8, and tip-end portions of the vanes 3 are brought into contactwith the cam face 4 a of the cam ring 4. With such a configuration, aplurality of pump chambers 6 are defined in the cam ring 4 by the outercircumferential surface of the rotor 2, the cam face 4 a of the cam ring4, and the adjacent vanes 3. The configuration of the vanes 3 will bedescribed in detail later.

The cam ring 4 is an annular member in which the cam face 4 a on theinner circumference has a substantially oval shape. The cam ring 4 hassuction regions 4 b in which volumes of the pump chambers 6, which aredefined between respective vanes 3 that slide on the cam face 4 a by therotation of the rotor 2, are increased and discharge regions 4 c inwhich volumes of the pump chambers 6 are decreased. As described above,respective pump chambers 6 are expanded/contracted by the rotation ofthe rotor 2. In this embodiment, the cam ring 4 has two suction regions4 b and two discharge regions 4 c.

As shown in FIG. 2, the pump cover 11 is arranged so as to be in contactwith the one side surface of each of the rotor 2 and the cam ring 4(upper side surface in FIG. 2), and a side plate 5 is arranged so as tobe in contact with the other side surface of each of the rotor 2 and thecam ring 4 (lower side surface in FIG. 2). The pump cover 11 and theside plate 5 are arranged in such a manner that both side surfaces ofeach of the rotor 2 and the cam ring 4 are sandwiched, and thereby, thepump chambers 6 are sealed.

On an end surface 11 a of the pump cover 11 on which the rotor 2 slides,the two arc-shaped suction ports (not shown) are formed so as torespectively open to the two suction regions 4 b of the cam ring 4 (seeFIG. 1) in a corresponding manner and to guide the working oil to thepump chambers 6. In addition, in the pump cover 11, a suction passage(not shown) through which a tank (not shown) is communicated with thesuction ports and that guides the working oil in the tank into the pumpchambers 6 through the suction ports is formed.

The side plate 5 has two arc-shaped discharge ports 20 that are formedso as to penetrate through the side plate 5 and open correspondingly tothe discharge regions 4 c of the cam ring 4.

In the pump body 10, a high-pressure chamber 21 into which the workingoil that has been discharged from the pump chambers 6 in the dischargeregions 4 c is guided is formed. The working oil that has beendischarged from the pump chambers 6 is guided the high-pressure chamber21 through the discharge ports 20 of the side plate 5. The working oilguided into the high-pressure chamber 21 is supplied to an externalhydraulic apparatus through a discharge passage (not shown) that isformed in the pump body 10 and is in communication with thehigh-pressure chamber 21.

In the side plate 5, two arc-shaped back pressure ports 22 that are incommunication with the high-pressure chamber 21 are formed. Each of theback pressure ports 22 communicates with the back pressure chambers 8.With such a configuration, the working oil in the high-pressure chamber21 is guided into the back pressure chambers 8 through the back pressureports 22.

With the vane pump 100, as the rotor 2 is rotated, the working oil issucked from the tank to each of the pump chambers 6 in the suctionregions 4 b of the cam ring 4 through the suction ports and the suctionpassage, and the working oil is discharged to the outside from each ofthe pump chambers 6 in the discharge regions 4 c of the cam ring 4through the discharge ports 20 and the discharge passage. As describedabove, in the vane pump 100, the working oil is supplied/discharged byexpansion/contraction of the respective pump chambers 6 caused by therotation of the rotor 2.

Next, the configurations of the vanes 3 will be specifically described.

As shown in FIG. 1, the plurality of vanes 3 have first vanes 3 a thatare formed by coating DLC (Diamond Like Carbon) on a base material andsecond vanes 3 b that are formed such that the base material is exposed.A state in which the base material is exposed means a state in which theDLC coating is not applied over the entirety of the vane 3 and thesurface of the base material remains exposed as the surface of the vane3.

The plurality of vanes 3 have two first vanes 3 a that are respectivelyinserted into the slits 7, which are adjacent to each other. Because thefirst vanes 3 a on which the DLC coating is applied have a superiorslidability, the viscous resistance of the working oil has less effecton the first vanes 3 a. Thus, even in the low-temperature situation inwhich the viscosity and the viscous resistance of the working oil arehigh, the first vanes 3 a project out from the slits 7 easily by therotation of the rotor 2. Thereby, one pump chamber (hereinafter referredto as “an initial pump chamber 6 a”) is defined by the adjacent firstvanes 3 a, and the starting performance of the vane pump 100 in thelow-temperature situation is improved.

In addition, because the initial pump chamber 6 a is defined by the twoadjacent first vanes 3 a, a part of the working oil discharged from theinitial pump chamber 6 a is guided into the back pressure chambers 8through the high-pressure chamber 21 and the back pressure ports 22.Thus, the second vanes 3 b on which the DLC coating is not applied arealso pushed into the directions in which the second vanes 3 b are drawnout from the slits 7 by the pressure in the back pressure chambers 8,and thereby, the second vanes 3 b project out from the slits 7 anddefine the pump chambers 6. As described above, because the initial pumpchamber 6 a is defined by the two first vanes 3 a, it is possible tofacilitate projection of other vanes 3 (the second vanes 3 b) from theslits 7, and so, it is possible to further improve the startingperformance in the low-temperature situation.

Although the first vanes 3 a have the superior slidability, because theDLC coating is applied on the base material, the cost required for themanufacture is high. Thus, if all of the plurality of vanes 3 are formedas the first vanes 3 a in order to improve the starting performance ofthe vane pump 100, the manufacturing cost of the vane pump 100 isincreased.

In contrast, in the vane pump 100, other ten vanes 3 than the two firstvanes 3 a are all formed as the second vanes 3 b. Even there are onlytwo adjacent first vanes 3 a, because the initial pump chamber 6 a isdefined by the first vanes 3 a at the starting time, the working oildischarged from the initial pump chamber 6 a is guided into respectiveback pressure chambers 8, and the projection of the second vanes 3 bfrom the slits 7 is facilitated. Thereby, the starting performance ofthe vane pump 100 is improved sufficiently. Therefore, by forming onlytwo adjacent vanes 3 of twelve vanes 3 as the first vanes 3 a, it ispossible to improve the starting performance of the vane pump 100 in thelow-temperature situation, and at the same time, it is possible tosuppress the increase in the manufacturing cost of the vane pump 100.

In addition, by applying the DLC coating, the wear resistance of thefirst vanes 3 a is also improved. Thus, the durability of the vane pump100 is also improved.

Next, a modification of the above-mentioned first embodiment will bedescribed.

In the above-mentioned first embodiment, the vane pump 100 has the twosuction regions 4 b and two discharge regions 4 c. Instead of thisconfiguration, the vane pump 100 may have one or at least three suctionregions 4 b and one or at least three discharge regions 4 c.

According to the first embodiment mentioned above, the advantagesdescribed below are afforded.

In the vane pump 100, because the sliding resistance of the first vanes3 a on which the DLC coating is applied is small, even in thelow-temperature situation, the first vanes 3 a project out from theslits 7 easily by the centrifugal force caused by the rotation of therotor 2. Thus, at the starting time of the vane pump 100, the initialpump chamber 6 a is formed easily by the adjacent first vanes 3 a.Therefore, it is possible to improve the starting performance of thevane pump 100.

In addition, in the vane pump 100, because the initial pump chamber 6 ais defined by the two adjacent first vanes 3 a, the working oil isguided into the back pressure chambers 8 through the high-pressurechamber 21 and the back pressure ports 22, and so, the second vanes 3 balso project out from the slits 7 and define the pump chambers 6. Asdescribed above, because the initial pump chamber 6 a is defined by thetwo first vanes 3 a, it is possible to facilitate projection of thesecond vanes 3 b from the slits 7, and so, it is possible to furtherimprove the starting performance in the low-temperature situation.

In addition, in the vane pump 100, even there are only two adjacentfirst vanes 3 a, because the initial pump chamber 6 a is defined by thefirst vanes 3 a at the starting time and the working oil is guided intothe respective back pressure chambers 8, the projection of the secondvanes 3 b from the slits 7 is facilitated. Therefore, by forming onlytwo adjacent vanes 3 of twelve vanes 3 as the first vanes 3 a, it ispossible to improve the starting performance of the vane pump 100 in thelow-temperature situation, and at the same time, it is possible tosuppress the increase in the manufacturing cost of the vane pump 100.

Second Embodiment

Next, a vane pump 200 according to a second embodiment of the presentinvention will be described with reference to FIG. 3. In the following,differences from the above-mentioned first embodiment will be mainlydescribed, and components that are the same as those in the vane pump100 in the above-mentioned first embodiment are assigned the samereference numerals and descriptions thereof will be omitted.

In the above-mentioned first embodiment, the two adjacent first vanes 3a are provided, and all the vanes 3 other than the first vanes 3 a areformed as the second vanes 3 b. Instead of employing this configuration,the vane pump 200 differs from that in the above-mentioned firstembodiment in that three first vanes 3 a are provided.

As shown in FIG. 3, the vane pump 200 has three first vanes 3 a and ninesecond vanes 3 b.

The three first vanes 3 a are arranged side by side in a consecutivemanner, and two initial pump chambers 6 a are respectively definedbetween the first vanes 3 a.

According to the second embodiment mentioned above, the advantagesdescribed below are afforded.

In the vane pump 200, similarly to the vane pump 100, because thesliding resistance of the first vanes 3 a on which the DLC coating isapplied is small, even in the low-temperature situation, the first vanes3 a project out from the slits 7 easily by the centrifugal force causedby the rotation of the rotor 2. Thus, at the starting time of the vanepump 200, the initial pump chambers 6 a are formed easily by theconsecutive three first vanes 3 a. Therefore, it is possible to improvethe starting performance of the vane pump 200.

In addition, in the vane pump 200, similarly to the vane pump 100,because the initial pump chambers 6 a are each defined by the twoadjacent first vanes 3 a, the working oil is guided into the backpressure chambers 8 through the high-pressure chamber 21 and the backpressure ports 22, and thereby, the second vanes 3 b also project outfrom the slits 7 and form the pump chambers. As described above, becausetwo initial pump chambers 6 a are defined by the three first vanes 3 a,it is possible to facilitate projection of the second vanes 3 b from theslits 7, and so, it is possible to further improve the startingperformance in the low-temperature situation.

In addition, in the vane pump 200, even at the starting time, the firstvanes 3 a project out from the slits 7 easily, and the projected firstvanes 3 a are pushed back into the slits 7 as they enter the dischargeregions 4 c. By the first vanes 3 a that are pushed back into the slits7, the working oil in the back pressure chambers 8 defined by thesefirst vanes 3 a is guided into the back pressure chambers 8 in theadjacent suction regions 4 b through the back pressure groove 8 a.Thereby, it is possible to further facilitate projection of the vanes 3in the suction regions 4 b.

In addition, in the vane pump 200, because two initial pump chambers 6 aare defined, it is possible to increase the flowing amount of theworking oil guided into the back pressure chambers 8 at the startingtime. Thus, it is possible to allow the second vanes 3 b to project outfrom the slits 7 with high reliability, and it is possible to furtherimprove the starting performance of the vane pump 200.

Third Embodiment

Next, a vane pump 300 according to a third embodiment of the presentinvention will be described with reference to FIG. 4. In the following,differences from the above-mentioned second embodiment will be mainlydescribed, and components that are the same as those in the vane pump200 in the above-mentioned second embodiment are assigned the samereference numerals and descriptions thereof will be omitted.

In the above-mentioned second embodiment, two initial pump chambers 6 aare defined by the consecutive three first vanes 3 a arranged side byside. Instead of employing this configuration, the vane pump 300 differsfrom that in the above-mentioned second embodiment in that the twoinitial pump chambers 6 a are defined by four first vanes 3 a.

As shown in FIG. 4, in the vane pump 300, the vanes 3 have four firstvanes 3 a and eight second vanes 3 b.

In the vane pump 300, the four first vanes 3 a are arranged such thatpairs of the adjacent first vanes 3 a face against each other with thecenter of the rotor 2 located therebetween. In other words, one initialpump chamber 6 a is defined by two adjacent first vanes 3 a, and twoinitial pump chambers 6 a that face against each other with the centerof the rotor 2 located therebetween are defined by the four first vanes3 a.

According to the above-mentioned third embodiment, in addition to theadvantages similar to those offered by the above-mentioned secondembodiment, the advantages described below are afforded.

In the vane pump 300, in a case where, in particular, the rotor 2 isprovided such that the central axis thereof is inclined from thevertical direction, a state in which a part of the vanes 3 are moveddownward in the vertical direction due to the gravitational force andare brought into contact with the cam face 4 a (a state in which thevanes 3 are projected out from the slits 7) may be maintained even whenthe operation is stopped. In the vane pump 300, because the two initialpump chambers 6 a that face against each other with the center of therotor 2 located therebetween are defined, when the operation is stopped,as compared with the case in the vane pumps 100 and 200 according to thefirst and second embodiments, the first vanes 3 a are more likely to belocated at the position where a state in which the first vanes 3 a areprojected out from the slits 7 is achieved (in particular, at the lowerportion in the vertical direction). Therefore, in the vane pump 300,even when the operation is stopped, the initial pump chamber 6 a islikely to be defined, and it is possible to further improve the startingperformance.

The configurations, operations, and effects of the embodiment of thepresent invention will be collectively described below.

The vane pumps 100, 200, and 300 include: the rotor 2 that is linked tothe driving shaft 1; the plurality of slits 7 that are formed in therotor 2 in a radiating pattern and have opening in the outercircumference of the rotor 2; the plurality of vanes 3 that arerespectively inserted into the plurality of slits 7 in a slidablemanner; the cam ring 4 that has the cam face 4 a on which the tip-endsof the vanes 3 slide by the rotation of the rotor 2; and the pumpchambers 6 that are defined by the rotor 2, the cam ring 4, and a pairof adjacent vanes 3. The plurality of vanes 3 have the plurality offirst vanes 3 a that are formed by applying the DLC coating on the basematerial and the second vanes 3 b that are formed such that the basematerial is exposed, and the first vanes 3 a are respectively insertedinto at least two adjacent slits 7 of the plurality of slits 7.

With this configuration, because the sliding resistance of the firstvanes 3 a on which the DLC coating is applied is small, even in thelow-temperature situation, the first vanes 3 a project out from theslits 7 easily by the centrifugal force caused by the rotation of therotor 2. Thus, at the starting time of the vane pumps 100, 200, and 300,the initial pump chamber 6 a is formed easily by the adjacent firstvanes 3 a. Therefore, the starting performance of the vane pumps 100,200, and 300 is improved.

In addition, the vane pumps 100, 200, and 300 further include the backpressure chambers 8 that are defined in the slits 7 by the base-endportions of the vanes 3 and into which the working oil discharged fromthe pump chambers 6 is guided.

With this configuration, because the initial pump chamber 6 a is definedby the two adjacent first vanes 3 a, the working oil is guided into theback pressure chambers 8, and the second vanes 3 b also project out fromthe slits 7 by the pressure of the working oil in the back pressurechambers 8 and define the pump chambers 6. As described above, becausethe initial pump chamber 6 a is defined by the two first vanes 3 a, itis possible to facilitate projection of the second vanes 3 b from theslits 7, and so, it is possible to further improve the startingperformance in the low-temperature situation.

In addition, in the vane pump 100, the plurality of vanes 3 have twofirst vanes 3 a.

With this configuration, even there are only two adjacent first vanes 3a, because the initial pump chamber 6 a is defined by the first vanes 3a at the starting time and the working oil is guided into the respectiveback pressure chambers 8, the projection of the second vanes 3 b fromthe slits 7 is facilitated. Therefore, by forming only two adjacentvanes 3 of the plurality of vanes 3 as the first vanes 3 a, it ispossible to improve the starting performance of the vane pump 100 in thelow-temperature situation, and at the same time, it is possible tosuppress the increase in the manufacturing cost of the vane pump 100.

In addition, the vane pump 200 has three first vanes 3 a, and the threefirst vanes 3 a are arranged side by side in a consecutive manner.

With this configuration, because two initial pump chambers 6 a aredefined, at the starting time, it is possible to increase the flowingamount of the working oil guided into the back pressure chambers 8.Thus, it is possible to allow the second vanes 3 b to project out fromthe slits 7 with high reliability, and thereby, it is possible tofurther improve the starting performance of the vane pumps 200 and 300.

In addition, the vane pump 300 has four first vanes 3 a, and the fourfirst vanes 3 a are arranged such that the pairs of the adjacent firstvanes 3 a face against each other with the center of the rotor 2 locatedtherebetween.

With this configuration, because the pairs of the adjacent first vanes 3a are arranged so as to face against each other with the center of therotor 2 located therebetween, even when the operation of the vane pump300 is stopped, it is likely that the first vanes 3 a are located at thelower portion of the rotor 2 in the vertical direction and the initialpump chamber 6 a is defined. Therefore, it is possible to furtherimprove the starting performance of the vane pump 300.

Embodiments of this invention were described above, but the aboveembodiments are merely examples of applications of this invention, andthe technical scope of this invention is not limited to the specificconstitutions of the above embodiments.

This application claims priority based on Japanese Patent ApplicationNo.2015-191667 filed with the Japan Patent Office on Sep. 29, 2015, theentire contents of which are incorporated into this specification.

1. A vane pump comprising: a rotor linked to a driving shaft; aplurality of slits formed in the rotor in a radiating pattern to open inan outer circumference of the rotor; a plurality of vanes respectivelyinserted into the plurality of slits in a slidable manner; a cam ringhaving an inner circumferential surface on which tip-ends of the vanesslide by rotation of the rotor; pump chambers defined by the rotor, thecam ring, and the pair of adjacent vanes, wherein the plurality of vaneshave: a plurality of first vanes formed by applying DLC coating on abase material; and a second vane formed such that the base material isexposed, and the first vanes are respectively inserted into at least twoadjacent slits of the plurality of slits.
 2. The vane pump according toclaim 1, further comprising back pressure chambers into which workingfluid discharged from the pump chamber is guided, the back pressurechambers being defined in the slits by base-end portions of the vanes.3. The vane pump according to claim 1, wherein the plurality of vaneshave the two first vanes.
 4. The vane pump according to claim 1, whereinthe plurality of vanes have the three first vanes, and the three firstvanes are arranged side by side in a consecutive manner.
 5. The vanepump according to claim 1, wherein the plurality of vanes have the fourfirst vanes, and the four first vanes are arranged such that pairs ofthe adjacent first vanes face against each other with a center of therotor located therebetween.